Fluid Flow Machine

ABSTRACT

A fluid flow machine has a stator, a rotor which is supported so as to be rotatable relative to the stator, and a brush seal which seals a gap formed between the stator and rotor in a radial direction to prevent the passage of fluid. The brush seal has a brush holder and a plurality of sealing bristles, each of which has a first end that is fastened to the brush holder and a second end that contacts a sealing surface. The sealing surface is rotationally displaceable relative to the second ends of the respective sealing bristles. The sealing surface is formed by a circumferential surface of an intermediate sleeve which is arranged between the stator and rotor and which radially divides the gap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a fluid flow machine with a stator,a rotor which is supported so as to be rotatable relative to the statorand a brush seal which seals the gap between the stator and the rotor inthe radial direction to prevent the passage of fluid.

2. Description of the Related Art

A fluid flow machine of the type mentioned above is known, e.g., from EP0 834 688 A1. An adjustable brush seal is known from U.S. Pat. No.6,435,514, the entire content of which is incorporated herein byreference.

Fluid flow machines include, for example, propellers and repellers,centrifugal pumps and turbo machinery of any kind such as gas turbines,steam turbines and rotary compressors such as, e.g., radial compressorsand axial compressors.

The rotor in fluid flow machines such as turbo machines can be sealed bymeans of labyrinth tip seals, mechanical seals or brush seals to preventthe leakage of fluid. In brush seals, sealing bristles (also known asbrush wires) of the brush seal make direct contact with the rotor of theturbo machine, this rotor being constructed, e.g., as a shaft. The brushseal limits the amount of work fluid, e.g., the amount of compressorair, flowing out of a flow part of the turbo machine into a bearingperiphery of the turbo machine, for example.

FIGS. 1 and 2 show a prior art fluid flow machine 1 which is constructedas a gas turbine. As can be seen from FIG. 1 and FIG. 2, the fluid flowmachine 1 has a stator 10 which is constructed in this instance as a gasturbine housing, a rotor 20 which is supported so as to be rotatablerelative to the stator 10 and which is constructed in this instance as ashaft, rotational bearings 30, 40 which carry out the rotatable bearingsupport of the rotor 20 in the stator 10, and two brush seals 50 whichseal a gap S formed in radial direction RR between the stator 10 androtor 20 to prevent the passage of fluid.

As can be seen particularly from FIG. 2, every brush seal 50 has a brushholder 51 and a plurality of sealing bristles 5, each of which has afirst end which is fastened to the brush holder 51 and a second endwhich contacts a sealing surface D which is formed in this case by anouter circumferential surface 21 of the rotor 20, so that a sealingbristle-on-sealing surface contact zone is formed. The sealing surface Dis rotationally displaceable, particularly rotatable in this case,relative to the second ends of the respective sealing bristles 52.

During operation of the fluid flow machine 1, the relative movementbetween the rotating rotor 20 and the brush seal 50, which is static inthis case, leads to heating of the sealing surface D of the rotor 20 andsealing bristles 52 due to the friction between the sealing bristles 52and the outer circumferential surface 21 of the rotor 20.

However, problems arise in this conventional seal in that an unevenheating of the sealing surface D is brought about in the absence of astate of true in the contact zone of the sealing surface D and sealingbristles 52. This uneven heating can exacerbate the out-of-true stateand lead to a deformation of the rotor 20 (manifesting itself in thiscase as sagging between the rotational bearings 30 and 40 of the shaft)which impairs continued operation of the fluid flow machine 1 owing toimpermissibly strong rotor vibrations.

It is an object of the invention to provide a fluid flow machine inwhich the sealing bristle-on-sealing surface contact zone is thermallydecoupled in order to prevent a deformation in the fluid flow machinewhich is brought about by introduced heat and which impairs theoperation of the fluid flow machine.

SUMMARY OF THE INVENTION

According to the present invention, a fluid flow machine has a stator, arotor which is supported so as to be rotatable relative to the stator,and a brush seal which seals a gap formed between the stator and rotorin a radial direction of the rotor to prevent the passage of fluid. Thebrush seal has a brush holder and a plurality of sealing bristles, eachof which has a first end that is fastened to the brush holder and asecond end that contacts a sealing surface so that a sealingbristle-on-sealing surface contact zone is formed. The sealing surfaceis rotationally displaceable relative to the second ends of therespective sealing bristles.

The fluid flow machine according to the present invention ischaracterized in that the sealing surface is formed by a circumferentialsurface of an intermediate sleeve or intermediate bushing which isarranged between the stator and rotor and which radially divides thegap.

By moving the sealing surface to an intermediate sleeve, the sealingbristle-on-sealing surface contact zone is thermally decoupled so as toprevent a deformation in the fluid flow machine which is brought aboutby introduced heat and which impairs the operation of the fluid flowmachine.

According to the present invention, the intermediate sleeve is fastenedeither to a rotating part or to a stationary part of the brush seal.This fastening is advantageously carried out in such a way that, on theone hand, sufficient stability is achieved and, on the other hand, aheat transfer between the intermediate sleeve and the part to which theintermediate sleeve is fastened is as small as possible. The small heattransfer can be achieved, e.g., by means of the smallest possiblecontact surfaces and/or by providing an insulating layer between thecontact surfaces of the intermediate sleeve and the part fastening thelatter.

According to the present invention, the brush holder can be arranged atthe stator and the intermediate sleeve can be arranged at the rotor soas to rotate along with the latter. In this case, the circumferentialsurface of the intermediate sleeve forming the sealing surface would bean outer circumferential surface. However, it is also possible accordingto the invention that the brush holder is arranged at the rotor and theintermediate sleeve is arranged in a stationary manner at the stator sothat the circumferential surface of the intermediate sleeve forming thesealing surface would be an inner circumferential surface in this case.The respective solution can be determined depending on the desiredoperating characteristics and design factors.

Further, according to the present invention, the rotor can be formed,e.g., by a shaft rotating in a stator (e.g., in a housing) and, e.g., bya housing rotating around a stator (e.g., around an axle). Therespective solution can be determined depending on the desired operatingcharacteristics and the design factors.

According to an embodiment of the invention, the intermediate sleevedivides the gap radially into a first gap portion adjoining the sealingsurface and a second gap portion adjoining a circumferential surface ofthe intermediate sleeve remote of the sealing surface, wherein a radialextension of the second gap portion is greater than zero.

In other words, there is an air gap between the intermediate sleeve andthe part (e.g., the rotor or the stator) fastening this intermediatesleeve. This air gap advantageously ensures additional thermalinsulation between the intermediate sleeve and the part fastening thesame. This makes it even more difficult for heat to transfer from thesealing surface and the part fastening the intermediate sleeve so that adeformation of the part fastening the intermediate sleeve that isbrought about by introduced heat is prevented in an even more reliablemanner.

According to another embodiment of the invention, the intermediatesleeve has a flange by means of which the intermediate sleeve is mountedat a flange mounting portion of the stator or rotor so as to be fixedwith respect to rotation relative to it.

This construction of the invention is advantageous particularly withrespect to ensuring the smallest possible contact surfaces between theintermediate sleeve and the part (in this case, particularly the statoror the rotor) fastening this intermediate sleeve, while at the same timeensuring that the fastening is sufficiently stable.

According to yet another embodiment of the present invention, the flangeis mounted at the flange mounting portion by detachable fastening means.Such fastening means can be, for example, screw connections, rivetconnections, clamping connections, etc. In particular, the detachableconnection facilitates the changing of worn intermediate sleeves, forexample.

Further, the flange connection makes it possible to introduce a thermalinsulation layer between the flange and the flange mounting portion in asimple manner.

According to another embodiment of the invention, the flange is arrangedat an axial end of the intermediate sleeve so that the flange has, atthe axial end, an annular flange surface which contacts a mountingsurface of the flange mounting portion so as to be tight against fluid.

This construction of the invention reliably ensures a seal between theintermediate sleeve and the part fastening this intermediate sleeve toprevent the passage of fluid.

According to another embodiment of the invention, the rotor is formed bya shaft and the intermediate sleeve is mounted on the rotor so as to befixed with respect to rotation relative to it so that the sealingsurface is formed by an outer circumferential surface of theintermediate sleeve, wherein the brush holder is arranged at the statorso as to be fixed with respect to rotation relative to it.

An embodiment of the invention of the kind mentioned above can beproduced in a particularly simple and dependably operating manner.

According to yet another embodiment of the invention, an inner diameterof the intermediate sleeve is greater than an outer diameter of theshaft so that an annular gap is formed between an inner circumferentialsurface of the intermediate sleeve and an outer circumferential surfaceof the shaft.

This construction of the invention achieves a thermally insulating airgap between the intermediate sleeve and the part fastening thisintermediate sleeve in a simple and robust manner, this part beingformed in this case by the rotor which is constructed as a shaft.

According to embodiment forms of the present invention, the fluid flowmachine is a turbo machine, particularly a gas turbine or a turbocompressor.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, and specific objects attained by its use,reference should be had to the drawing and descriptive matter in whichthere are illustrated and described preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following withreference to preferred embodiments and the accompanying drawings inwhich:

FIG. 1 is a schematic sectional view of the basic construction of afluid flow machine constructed as a gas turbine according to the priorart;

FIG. 2 is an enlarged section A from FIG. 1 showing a brush seal of afluid flow machine according to the prior art; and

FIG. 3 an enlarged section A′ from FIG. 1 showing a brush seal of afluid flow machine according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

As is shown in FIGS. 1 and 3, a fluid flow machine 1 which isconstructed in this instance as a gas turbine has a stator 10 which isconstructed in this instance as a gas turbine housing, a rotor 20 whichis constructed in this instance as a shaft which is mounted so as to berotatable relative to the stator 10, two rotational bearings 30, 40which form the rotatable bearing support of the rotor 20 in the stator10, and two brush seals 50′ which seal a gap S which is formed in aradial direction RR between the stator 10 and rotor 20 so as to beprevent the passage of fluid.

As can be seen particularly from FIG. 3, every brush seal 50′ has abrush holder 51 and a plurality of sealing bristles 52 each of which hasa first end fastened to the brush holder 51 and a second end contactinga sealing surface D′ so as to form a sealing bristle-on-sealing surfacecontact zone, the sealing surface D′ being displaceable with respect torotation, particularly rotatable in this instance, relative to thesecond ends of the respective sealing bristles 52.

As can be seen from FIG. 3, the sealing surface D′ is formed by an outercircumferential surface 61 of an intermediate sleeve 60 which isarranged between the stator 10 and rotor 20 and which is mounted on therotor 20 so as to be fixed with respect to rotation relative to it andso as to divide the gap S radially. The brush holder 51 is arranged atthe stator 10 so as to be fixed with respect to rotation relative to it.

The intermediate sleeve 60 divides the gap S radially into a first gapportion adjoining the sealing surface D′ and a second gap portionadjoining an inner circumferential surface D″ of the intermediate sleeve60 remote of the sealing surface D′. A radial extension of the secondgap portion is greater than zero.

This means that an inner diameter of the intermediate sleeve 60 isgreater than an outer diameter of the rotor (shaft) 20 so that anannular gap LS is formed between the inner circumferential surface ofthe intermediate sleeve 60 and an outer circumferential surface 21 ofthe rotor 20.

In other words, an air gap (annular gap) LS is provided between theintermediate sleeve 60 and the rotor 20 fastening the latter, which airgap advantageously ensures a thermal insulation between the intermediatesleeve 60 and the rotor 20. This makes it more difficult for heat to betransferred from the sealing surface D′ to the rotor 20, which preventsa deformation of the rotor 20 fastening the intermediate sleeve 60 dueto introduced heat.

Further, as can be seen from FIG. 3, the intermediate sleeve 60 has aflange 62 by means of which the intermediate sleeve 60 is mounted at theflange mounting portion 22 of the rotor 20 so as to be fixed withrespect to rotation relative to it. The flange 62 is arranged at anaxial end of the intermediate sleeve 60 so that the flange 62 has, atthe axial end, an annular flange surface 62′ which contacts a recessedmounting surface (not designated separately) of the flange mountingportion 22 in a fluid-tight manner. Although not shown in FIG. 3, a flatseal can be provided for achieving the fluid tightness and a thermalinsulation between the annular flange surface of the flange 62 and therecessed mounting surface of the flange mounting portion 22.

As is shown in FIG. 3, the flange 62 is mounted at the flange mountingportion 22 of the rotor 20 by detachable fastening means which arerealized in this instance in the form of a screw connection.

In conclusion, the rotor 20 which is constructed in this instance as ashaft is provided with an intermediate sleeve or intermediate bushing 60according to an embodiment of the invention. The intermediate sleeve 60is connected to the rotor 20 by means of an axial flange 62 anddetachable fastening means. There is an annular gap LS between theintermediate sleeve 60 and the rotor 20. The sealing bristles or brushwires 52 of the brush seal 50′ contact the sealing surface D′ formed bythe outer circumferential surface 61 of the intermediate sleeve 60.

Accordingly, in the event of an out-of-true state of the intermediatesleeve 60, an uneven deformation of the intermediate sleeve 60 may onlyaggravate the out-of-true state of the intermediate sleeve 60 becausethe rotor 20 is only connected to the intermediate sleeve 60 by theconnection of its flange mounting portion 22 to the flange 62 so that adirect heating of the rotor 20 caused by heat entering the area of thebrush seal 50′ is prevented.

The solution according to the invention can be applied wherever a fluidflow machine, e.g., a gas turbine, is to be sealed with brush seals. Theinvention can be applied, e.g., in disk rotor units, full rotor unitsand welded rotor units.

The solution according to the invention can be used to seal a bearingperiphery of a fluid flow machine and to seal between individual stagesof the fluid flow machine, e.g., compressor stages or turbine stages.

Apart from the flange connection described above, fastening of theintermediate sleeve to the part which fastens or holds it can also becarried out by means of shrinking or welding or by means of otherfastening elements.

The invention is not limited by the embodiments described above whichare presented as examples only but can be modified in various wayswithin the scope of protection defined by the appended patent claims.

1. A fluid flow machine comprising a stator (10), a rotor (20) supportedso as to be rotatable relative to the stator (10), said stator and rotordefining a gap (S) therebetween in a radial direction (RR); a brush seal(50′) for sealing said gap (S) between said stator and said rotor toprevent a leakage of fluid, said the brush seal comprising a brushholder (51) and a plurality of sealing bristles (52); a sealing surface(D′) in contact with said sealing bristles; each sealing bristle havinga first end fastened to said brush holder (51) and a second endcontacting said sealing surface (D′); said sealing surface (D′) beingrotationally displaceable relative to said second ends of saidrespective sealing bristles (52); said sealing surface (D′) being formedby a circumferential surface of an intermediate sleeve arranged betweensaid stator (10) and said rotor (20) for radially dividing said gap (S).2. The fluid flow machine according to claim 1, wherein saidintermediate sleeve (60) divides said gap (S) radially into a first gapportion adjoining said sealing surface (D′) and a second gap portionadjoining a circumferential surface of said intermediate sleeve (60)remote of said sealing surface (D′), and wherein a radial extension ofsaid second gap portion is greater than zero.
 3. The fluid flow machineaccording to claim 1, additionally comprising a flange mounting portion(62) at one of said stator and said rotor and wherein said intermediatesleeve (60) comprises a flange (62) for mounting said sleeve (60) atsaid flange mounting portion (22) of one of said stator (10) and saidrotor (20) so as to be fixed with respect to rotation relative thereto.4. The fluid flow machine according to claim 3, wherein said flange (62)is detachably mounted at said flange mounting portion (22).
 5. The fluidflow machine according to claim 3, wherein said flange (62) comprises anannular flange surface at an axial end thereof and said flange mountingportion (22) comprises a mounting surface; and wherein said flange (62)is arranged at an axial end of said intermediate sleeve (60) so thatsaid annular flange surface is contacting said mounting surface of saidflange mounting portion (22) so as to be tight against fluid.
 6. Thefluid flow machine according to claim 1, wherein said intermediatesleeve (60) comprises an outer circumferential surface (61) and whereinsaid rotor (20) is formed by a shaft, and said intermediate sleeve (60)is mounted on said rotor (20) so as to be fixed with respect to rotationrelative thereto so that said sealing surface (D′) is formed by an outercircumferential surface (61) of said intermediate sleeve (60), andwherein said brush holder (51) is arranged at said stator (10) so as tobe fixed with respect to rotation relative thereto.
 7. The fluid flowmachine according to claim 6, wherein said intermediate sleeve (60)comprises an inner diameter and an inner circumferential surface; andsaid shaft comprises an outer diameter and an outer circumferentialsurface (21) and wherein said inner diameter of said intermediate sleeve(60) is greater than said outer diameter of said shaft so that anannular gap is formed between said inner circumferential surface of saidintermediate sleeve (60) and said outer circumferential surface (21) ofsaid shaft.
 8. The fluid flow machine according to claim 1, wherein saidfluid flow machine is a turbo machine.
 9. The fluid flow machineaccording to claim 8, wherein said turbo machine is one of a gas turbineand a turbo compressor.